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    Subject[PATCH for-next 16/25] fortify: Explicitly disable Clang support
    Date
    Clang has never correctly compiled the FORTIFY_SOURCE defenses due to
    a couple bugs:

    Eliding inlines with matching __builtin_* names
    https://bugs.llvm.org/show_bug.cgi?id=50322

    Incorrect __builtin_constant_p() of some globals
    https://bugs.llvm.org/show_bug.cgi?id=41459

    In the process of making improvements to the FORTIFY_SOURCE defenses, the
    first (silent) bug (coincidentally) becomes worked around, but exposes
    the latter which breaks the build. As such, Clang must not be used with
    CONFIG_FORTIFY_SOURCE until at least latter bug is fixed (in Clang 13),
    and the fortify routines have been rearranged.

    Update the Kconfig to reflect the reality of the current situation.

    Signed-off-by: Kees Cook <keescook@chromium.org>
    ---
    security/Kconfig | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/security/Kconfig b/security/Kconfig
    index 0ced7fd33e4d..fe6c0395fa02 100644
    --- a/security/Kconfig
    +++ b/security/Kconfig
    @@ -191,6 +191,9 @@ config HARDENED_USERCOPY_PAGESPAN
    config FORTIFY_SOURCE
    bool "Harden common str/mem functions against buffer overflows"
    depends on ARCH_HAS_FORTIFY_SOURCE
    + # https://bugs.llvm.org/show_bug.cgi?id=50322
    + # https://bugs.llvm.org/show_bug.cgi?id=41459
    + depends on !CC_IS_CLANG
    help
    Detect overflows of buffers in common string and memory functions
    where the compiler can determine and validate the buffer sizes.
    --
    2.30.2
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